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Chemistry

A Level

why does silicon dioxide have such a high melting/boiling point?

It has a giant lattice structure, strong covalent bonds are difficult to break etc.

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1. X with 2,4-DNPH forms a red precipitate. 2. X reduces blue Copper ions into red precipitate. What kind of compound is X?

X with 2,4 DNPH (Brady's reagent) is used to show the presence of an aldehyde or ketone. X also reduces Copper ions (Fehling's) meaning it has to be an aldehyde and not a ketone as ketones are not readily...

Answered by Tom A. • Chemistry tutor

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Elemental analysis of a carbohydrate X showed the sample contained 48.7 % carbon and 8.1 % hydrogen by mass. Find the empirical formula of X.

These sorts of questions can look difficult, but if you learn the steps needed to solve them then they are all very similar.Step 1: Since we are told that X is a carbohydrate, we know tha...

Answered by Jack B. • Chemistry tutor

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Explain the trend in ionisation energies for the group one metals?

The first ionisation energy of an element is the minimum energy required to remove a single electron from one mole of an element in its gaseous state. As you go down the group the first electron becomes e...

Answered by Dan C. • Chemistry tutor

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X, a gas, has a mass of 0.270g and is present in a gas syringe with a volume of 105.0cm^3 at 97C and 100kPa. Calculate the Mr of X. (5 marks)

This is a classic A-level question which uses the formula:PV=nRT First, this equation (which needs to be learnt, it is not given in the exam papers) must be rearranged to:n=PV/RTWhat all these letters in ...

Answered by Jack B. • Chemistry tutor

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